Several things I found interesting for a retrace deck:Retrace cards (duh), mainly red/green eg.:Calll the SkybreakerFlame JabWaves of AgressionMonstrifySavage ConceptionWorm HarvestSpitting Image

Possibly more lands than in a ususal deck, maybe 28 or so. Some of these lands are in form of karoos, so that you can tap a land for mana, bounce it when you play a karoo (essentially increasing its productivity by 1 next turn), then discard it to retrace.

Life from the Loam adds a mice touch, returning lands from your graveyard to retrace, and dredging to put retrace spells in your graveyard.

Scouting Trek is excellent late-game, as it fetches all your lands, and grants you a retrace spell every turn. (Worm Harvest)